I did so too. It is an excellent tool to understand orbital mechanics and manouvers. Stat-wise it's not its forte but I ran mods that told you anything what you desire in numbers to crunch.
ED Ships vs. RL Rockets
- Thread starter Old Duck
- Start date
Absolutely, yes (to the first part).
If you haven't played KSP, you really should.
It starts off really simple, giving you straightforward missions which you'll probably only fail because you've either built a ship that's too heavy or because you've done something stupid (such as, say, fitting all the batteries to a section of the ship that gets jettisoned and leaves you with a ship you can't control).
You, basically, learn by trial and error (which is what Kerbals do) and then you can take on more and more difficult missions which take advantage of what you've learned.
You will fail a lot (like, for example, successfully landing a ship on the Moon and then realising you don't have enough fuel to get home again, or that your ship burns up in the atmosphere upon re-entry) but everything you do teaches you something, and gives you new ideas for what to try next time.
It's like the world's best puzzle-game, with cartoon rockets and little vegetable-people.
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Essentially you will learn that fuel is its own dead weight and needs more thrust and even more guel to be moved.
You'll be glad AND annoyed once you burned off most of it in general.
You'll be glad AND annoyed once you burned off most of it in general.
Oh. And you'll learn to love nukes. As in nuclear propulsion engines. All hail the 800 ISP Nerv.
That's a thing you'll learn too. ISP rules.
And going back to ED: the ED spaceships seem to have a propulsion system based on ion (or plasma - basically the same) thrusters. The rocket equation still holds true (you can't cheat physics that easily), but your exhaust velocity is gigantic. The Wikipedia article about spacecraft propulsion has a nice table somewhere down the page - the exhaust velocity of a good solid rocket booster is quoted at 1 km/s, while the exhaust velocity of a contemporary ion thruster is around 50 km/s. Since everything in spacecraft propulsion depends on that exhaust velocity (and sometimes on its square), you can see (or calculate) that those ion thrusters will give a lot of whoosh per mass. In ED so much, that teh fuel consumption of your real space engines is almost negligible compared to that of a FSD jump.
If you don't reach escape velocity, your current-technology rocket's limited supply of chemical fuel will sooner or later run out and the gravity well will pull you back in, possibly for a less-than-gracious landing, unless your intent is to establish an orbit around the launch planet.I've got a simple science question for those of you who are experts in this field. In ED, we can "slow burn" our way from a planet's surface into outer space if we're patient enough (not using supercruise). Why can't we do this in real life? Why do our rockets need to reach incredibly high escape velocities, being the hare instead of the turtle?
My assumption is it's a combination of efficiency (it uses less fuel to burn hard and fast over a short period of time than it would to go slow and steady over a long period of time) and the need to reach an orbital velocity. To the latter point, how far does one need to go before you no longer need a high orbital velocity to prevent falling back towards the earth?
Anyway, I was just thinking on these things and wondering why we can't "slow burn" our way to, say, the moon for example. I realize this is grade school science for some of you, so please take it easy on the aerospace virgin that I am
For me, "phase 3" of all my KSP shenanigans is always building a refuelling station in orbit around Kerbin.
Phase 1 & 2 is just about getting ships out into space but once I'm doing that reliably I always launch a small station (usually for a mission) and then expand it by fitting huge, empty, tanks to it.
I'll put it in an equatorial orbit, on the opposite side of Kerbin to the KSC, and then all my returning ships can dock there, dump their surplus fuel and then undock, do a quick de-orbit burn and then land on the surface somewhere near the KSC.
Once I've got my refuelling station in orbit, it gives me a lot more latitude to launch heavy payloads without worrying about carrying enough fuel to get to, say, Duna.
It's not just a matter of burning fuel quickly to leave the gravity well as fast as possible, there is also another very important factor at play here - the atmosphere.
Burning all the fuel in a millisecond would definitely get you up to a high speed very quickly, but air resistance scales with the square of the velocity. Because of this square, doubling the movement speed causes 4 times the drag, which in turn reduces the efficiency of the launch.
This is why rockets are always playing a very delicate balancing act during launch. They don't want to fly too slowly as then they are burning too much fuel to overcome gravity; they don't want to fly too quickly as then they are burning too much fuel to overcome air resistance. In fact, the ideal ascent velocity for a rocket in terms of efficiency is equal to its terminal velocity (the maximum speed it will reach in free-fall).
Also, attempting to burn fuel immediately (like in a space cannon) doesn't really improve final velocities that much, as fuel only contains a certain amount of potential energy and so there are strongly diminishing returns on trying to force an object to go faster than a certain point using rapid combustion. This is also without getting into the practical limits regarding shockwave propagation at high speeds when trying to propel things.
Fair comment.
I was going to mention atmospheric drag but that's really only specific to a minority of planets (or, in ED, none).
You're right, though.
It is something that needs to be considered.
Even if it was possible, there'd be no point in generating all your thrust instantly and then losing some of that thrust as your ship forces it's way through a dense atmosphere.
In practical terms, on Earth, I'm not sure it's actually much of a problem because we simply don't have a fuel-source that's light enough, or provides enough energy, and we don't have engines powerful enough either, that we have to worry about generating the thrust too quickly.
Also, at our level of technology, it's not really something we'd ever be concerned about because if it was easier to get through an atmosphere and into orbit, we'd simply build ships with smaller fuel tanks and so the status quo would remain.
If we were carrying out the sort of missions we do in ED, though, where we've got ships that are refuelling and then launching on missions that might take them to multiple places without refuelling again, launching your ship in the most efficient manner would definitely be something that'd require a bit of thought.
In addition to KSP, Pioneer Space is a good game to have a look at as a bridge between KSP and Frontier Elite 2, which shows your dV and how ship, cargo and fuel mass effects it but with the Sci Fi super engines, so you can get a feeling for how "advanced" they are to what you can build in KSP
Deleted member 38366
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So... you're basically just waiting for getting a "approaching max q" notification, followed shortly by a "clear for Throttle-up" when leaving a Planet?
Landable Atmospheric Planets for the new era.So... you're basically just waiting for getting a "approaching max q" notification, followed shortly by a "clear for Throttle-up" when leaving a Planet?
Pretty much everything I know about rocketry, I learned on Atomic Rockets. Awesome site. ^^
ED engines - even the thrusters - are apparently reactionless drives. Since you don't seem to use up ANY propellant. That might also be the reason why we're confined to such pitiful relative velocities that are more comparable to WW2 planes than to rocketships.
I've got a simple science question for those of you who are experts in this field. In ED, we can "slow burn" our way from a planet's surface into outer space if we're patient enough (not using supercruise). Why can't we do this in real life? Why do our rockets need to reach incredibly high escape velocities, being the hare instead of the turtle?
My assumption is it's a combination of efficiency (it uses less fuel to burn hard and fast over a short period of time than it would to go slow and steady over a long period of time) and the need to reach an orbital velocity. To the latter point, how far does one need to go before you no longer need a high orbital velocity to prevent falling back towards the earth?
Anyway, I was just thinking on these things and wondering why we can't "slow burn" our way to, say, the moon for example. I realize this is grade school science for some of you, so please take it easy on the aerospace virgin that I am
Worth noting that even a slowish ship, say a boosting corvette at 360m/s is still doing a supersonic mach 1.05, so its "slow burn" isnt that slow, sure its not straight into robital speeds like a flacon 9's mach 6 (2040m/s).
In the 20th century we had sent aeroplanes to the stratosphere, using nothing more than a jet engine at subsonic speeds, think U2 / SR71 / Phantom F4 / MIG 25, the limit of around 125,000ft seems to be where jet engines stop providing any thrust. Were we to try such things in a hyrbid rocket jet like an english electric lightning, or some of the new hypersonic planes in development, there is no reason we couldn't get orbital in a plane.
The restriction on current rockets having to make their velocity PDQ comes down to fuel, in elite our thrusters vent superhot plasma from our reactors as really high energy high velocity propellant, think of them a super mega ahll effect thrusters. Where as a contrmporary rocket can only vent its combustion products, given that the exhaust velocity is the key to creating thrust, because we are using plasma, even better than ionised gas like sattelites use, the ships in ED can sustain longer burns. Because of the inherent energy of our reactor plasma, and its electric magnetic acceleration, it has a very high "specific impulse" But because of the way the propellant is generated in the reactor as opposed to being stored in tanks, we cannot support furious burns like a falcon 9 or any other rocket.
I need to play KSP, as it is widely recognised as being valid rocket sceince cirriculum wrapped up in a game, and would be a good way for me to fill in some of the gaps in my knowledege.
Just done a test on my cutter which seems to reach 250m/s in almost exactly 10 seconds. That is 2.5g .
Subtracting earths 1g gravity, that would mean it accelerates upwards at 1.5g . In fact, that is not much more than a military jet can achieve today.
So a jet could fly into space at the same speed as a cutter if it could breathe air all the way.
Or turn into a rocket when the air runs out like this ...
en.wikipedia.org
Subtracting earths 1g gravity, that would mean it accelerates upwards at 1.5g . In fact, that is not much more than a military jet can achieve today.
So a jet could fly into space at the same speed as a cutter if it could breathe air all the way.
Or turn into a rocket when the air runs out like this ...
SABRE (rocket engine) - Wikipedia
Pretty much this.
More mass you need to break out to orbit the more fuel you need.
Fuel has mass, which needs more fuel to lift. See the challenge?
This problem is basically not represented in the game.... and so if we had a real life, virtually mass-less fuel source, we could make rockets that fly the same as elites ships.